1. Field of the Invention
The present invention relates to well drilling tools and, more particularly, to a tool for extracting solid particles, such as sand and debris, from a well hole.
2. Description of the Related Art
It is well-known in the well bore formation art that debris is an unwanted by-product of sand fracturing, drilling out, natural formation fill-up, etc. In some wells, circulating this debris to the surface is not feasible due to loosing circulation into weak zones, or it is not cost-effective. For example, in order to clean out debris from a low fluid level well, an air unit or nitrogen unit is required to blow the debris out. Both methods are expensive and not environmentally friendly.
A reciprocating sand pump could be run into the well bore. Such a pump usually requires a significant amount of fluid in the well to allow the pump to move up and down through the fluid. Also, if the debris is hard, the reciprocating pump has difficulty picking up the debris. That is, one must drill a few inches then stroke the pump, and keep repeating this operation.
In light of the above, a need exists for a well bore tool that is capable of removing solid particles from the well bore with greater efficiency and reliability.
Accordingly, it is a purpose of the present invention to provide a well tool that does not have to be raised and lowered in a column of water to operate, thereby requiring very little fluid to remove the solid particles.
It is also a purpose of this invention to provide a well tool which prevents sand, debris, etc., entering the tool from clogging the tool.
It is another purpose of the present invention to provide a well tool that eliminates the need for expensive and environmentally unfriendly air or hydrogen blow outs.
It is another purpose of the present invention to provide a pump that can be run into a well bore to remove debris left behind after sand fracturing, etc., even in wells where circulating debris to the surface is not feasible, or is not cost effective.
To achieve the foregoing and other purposes of the present invention there is provided a well tool including: a flapper valve assembly above a drill bit; a sand screen; and a screw pump. The tool is used for removing unwanted solid materials, such as sand, left in a hole after sand fracturing, drilling, etc. The fluid in the hole, with the solid particles therein, is pumped into the device past the bit, by rotating the tool which rotates the pump, and across the flapper valve assembly. Only the fluid then moves through the holes in the sand screen, and the solid particles stay in a cavity formed above the flapper valve. The fluid moves along the screw pump and is returned downward along the outside of the tool to the bit, to start the cycle over again. Over time, the cavity collects the solid particles therein and the device is raised to the surface, where the accumulated solid particles are dumped, and the device is re-introduced into the hole to remove more solid particles, if necessary.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.